1. Field of the Invention
The present invention concerns a method for generation of an angiographic image by magnetic resonance, as well as a magnetic resonance apparatus for implementation of such a method.
2. Description of the Prior Art
Magnetic resonance technology has been increasingly used in recent years to generate angiographic images since, relative to other medical imaging modalities such as, for example, radioscopy with x-rays or computed tomography, it has among other things, the advantage that patient and medical personal are subjected to no radiation exposure.
Magnetic resonance (MR) technology is a known technology with which images of the inside of an examination subject can be generated. For this purpose, the examination subject is positioned in a strong, static, homogeneous basic magnetic field (field strengths of 0.2 Tesla to 7 Tesla and higher) in an MR apparatus so that the subject's nuclear spins become oriented along the basic magnetic field. Radio-frequency excitation pulses are radiated into the examination subject to excite nuclear magnetic resonances, the excited nuclear magnetic resonances being measured (detected and MR images being reconstructed based thereon. For spatial coding of the measurement data, rapidly switched magnetic gradient fields are superimposed on the basic magnetic field. The acquired measurement data are digitized and stored as complex numerical values in a k-space matrix. An associated MR image can be reconstructed from the k-space matrix populated with such values by means of a multi-dimensional Fourier transformation.
Magnetic resonance technology can thereby also be used in magnetic resonance angiography (MRA) to generate an angiograph with the use of a special MR pulse sequence suitable for this purpose. Known MRA techniques are, for example, time-of-flight (TOF) angiography and phase contrast angiography.
Another possibility to generate an angiograph with the use of magnetic resonance technology involves the use of a contrast agent, for example based on gadolinium. The contrast agent is injected into the vascular system of a patient so that it highlights the structures of the vascular system relative to surrounding tissue after subsequent propagation in the vascular system.